We describe an unusual case of a patient with polysplenia, inferior vena cava (IVC) interruption, and unrecognized congenital portosystemic venous connection (CPVC) in whom severe cyanosis developed in the acute postoperative stage after a Kawashima operation and required urgent surgical division of the CPVC. It has been stressed recently that CPVCs and other abdominal venous abnormalities have been underdiagnosed in patients with polysplenia and IVC interruption, and we think that a routine evaluation of abdominal venous connections should be mandatory before considering the Kawashima operation for these patients.